The amygdala and nucleus accumbens have long been recognized as structures important for the control over behavior by reinforcing and motivational stimuli. More recent work suggests that the basolateral complex of the amygdala (BLC) and the accumbens, to which it projects strongly and unidirectionally, function as a system involved in the processing of acquired stimulus value information. However, several questions remain regarding the functions of this system, including whether it is involved in learning processes or simply behavioral expression of learned information, and whether it is equally important for processing of appetitive and aversive stimulus value information. The proposed experiments will investigate the nature of the involvement of the BLC and accumbens in these functions. Specific Aim 1 will use an appetitive second-order conditioning task (which allows assessment of the degree to which a stimulus has acquired motivational value), to determine whether the BLC and accumbens are involved in learning or performance of appetitive stimulus value information. Specific Aim 2 will use an aversively motivated second-order conditioning task to determine whether the accumbens is involved in processing of aversive stimulus value, and if so, in what capacity. Specific Aim 3 will use in vivo electrophysiology to investigate how appetitive and aversive stimulus value are encoded in accumbens neuronal responses, and the degree to which this encoding is dependent on the BLC. It is hoped that these complementary approaches will enable a more complete understanding of how these structures function together to influence motivated behavior in both normal and disease states.